Dyed cellulose ethers and dyeing of fabrics therewith



Patented Sept. 7, 1948 DYED CELLULOSE ETHERS AND DYEING F FABRICS THEREWITH William 3. Carroll, Jr.. Schoolfleld, val, asslgnor to Dan River Mills, Incorporated, a corporation of Virginia No Drawing. Application September 5, 1947, Serial No. 772,459

9 Claims. (01. 117-168) This appllcatlom is a continuation-impart of my copending application Serial No. 547,814, which was filed August 2, 1944, allowed May 22, 1947, and forfeited November -22, 1947.

The invention herein relates to dyeing of textile materials, and to dye solutions therefor. More particularly, it provides the answer to an age old problem in the dyeing art of uniformly dyeing piece goods, especially in short lengths, so as to obtain the same shade in the dyed cloth from one end to the other. The successful method comprises applying the dye to a. carrier, namely, a cellulose ether, which,satisfies the usual varying afllnities of the dye for the cellulose of the cloth, then dissolving the dyed cellulose ether in a suitable alkali to produce the dye solution, and finally applying this solution to the cloth and precipitating the predyed cellulose ether onthe cloth by souring with acid.

An important feature of this method is to dye the cellulose ether in its natural, solid form and thereby produce a dyed solid cellulose ether which can then be dissolved in alkali. If the cellulose ether is first dissolved in alkali and then the dye added to the solution, the characteristic results of this invention will not be obtained.

In this method, the alkali solution of predyed cellulose ether has no varying or selective ailinity for the cloth to which it is applied. In fact, the cloth so treated is not dyed in the usual sense of the term because the usual ailinity of the dye for cellulose has already been satisfied in the predyeing of the cellulose ether. Accordingly, the alkali solution of predyed cellulose ether does notreact" with the cellulose of the cloth and cause the variations in shade thatnormally occur in the usual dyeing operation and in which the dye does react with the cellulose.

All that is required when using the alkali solution of predyed cellulose ether, is to attach the dyed cellulose ether onto the cloth. This is accomplished very simply by a souring operation in which the treated cloth is run into an acid bath. The acid causes a precipitation. out of solution of the dyed cellulose ether which is soluble only in an alkaline medium. The precipitated, dyed, cellulose ether attaches quickly and permanently to the cloth or other textile material being dyed. 7

One of the unique and unexpected properties of the alkali solution of predyed cellulose ether is that the components of the solution are very firmly held together; in fact, so much so that they do not separate to any substantial extent 2 even when centrifuged. This indicates that the dye has either reacted with. or very strongly attached itself to the cellulose ether in some unexplainable manner. It would normally be expected that the dye and cellulose ether would separate upon being dissolved in the alkali or at least when the alkali solution thereof is centrifuged. This strong, permanent cohesion between the dye and the cellulose ether makes the alkali, solution thereof especially suitable for uniformly dyeing the textile material to the same shade throughout the length of the material.

This alkali solution of the dyed cellulose ether is particularly beneficial in the dyeing of piece goods of relatively short lengths, such as, -1000 yards. which are commonly dyed by the jig method. Jig dyeing is one of the oldest and yet one of the most practical methods in use today for dyeing piece goods of a few yards in length up to 500-1000 yards in length. At the same time, jig dyeing is plagued with variations in shade of the piece goods dyed by this method. Results on rolls of 100 to 1000 yards are considered excellent if the finished cloth can be divided into three shades, representing the two ends and the middle of the roll, especially when dyeing vat colors on piece goods.

The use of vat dyes further complicates the problem of variations in shade encountered with jig dyeing, and requires great skill on the part of the operator to produce commercially satisfactory results. The old difliculty of shading from end to end and in the middle of the roll still persists and in fact is accentuated, for not only do the vat dyestuffs attach themselves rapidly to the fiber but once attached they refuse to be moved, so that evening up of the shade by continuing the dyeing operation, which can be accomplished to a certain extent with the less fast sulfurs and directs, has very little efiect.

One of the early attempts to get away from the difficulties of jig dyeing of vat colors is what is generally termed the reduced pad method, which depends on reducing the vat dyestufis before applying them to the textile material. These dyestuffs in their completed state are insoluble.

organic pigments with little, if any, afllnity for textle fibers. Added to a bath of alkali and hydrosulfite of sodium they are reduced and dissolved and in this condition act as true dyestuffs; i. e, they are preferentially adsorbed by various fibers and particularly by cellulose.

The equipment used in the reduced pad method consists of a very small dye box attached to a pad of two heavy squeeze rollers. This small box is charged with the soluble reduced dyestui! and the cloth passed rapidly through it and on through the squeeze rollers and allowed to fold The principal weakness of this method is the short contact of the cloth with the reduced dyestuil'. The dyestui! has no more than attached itself to the fiber when it begins to oxidize without actually becoming an integral part of the,

fiber. In other words, it is more or less of a so-called "surface dyeing" and some twenty to thirty per cent of it washes of! in the first soaping.

In more recent years the "continuous dyeing methods and machines have been introduced but they are very expensive and are designed for dyeing long lengths of cloth, such as 100,000 yards and up. They are not suited for dyeing short lengths of 100 to 1000 yards.

Despite all of the improvements which have taken place in the dyeing art since the beginning of Jig dyeing and reduced pad dyeing, the problem of shade variation has continued to the present time and has been the woe of the dyer of piece goods in lots of less than 1000 yards. Consequently it has been impossible for the jig dyer to obtain uniformity of color or to predict with any assurance the exact shade that he would get on the jig even though it was obtained accurately in advance in a laboratory dye test. Up to the time of the present invention there was positively no known method of producing a satisfactory predetermined shade on fabrics in small yardages. This is especially true when using vat dyes in pastel shades. The apparent dominating cause of this whole difficulty is the selective afllnity of the dye for the cellulose and the consequent varying reaction of the dye therewith so that the cloth absorbs or takes up varying amounts of the dye over a given length and results in shade variations.

In accordance with the present invention, these long standing difficulties in the dyeing art are overcome by the use of the alkali solution of predyed cellulose ether as outlined hereinabove. In this method there is no reaction between the dyestuff and the cloth because the dyeing reaction has already taken place in the predyeing of the cellulose ether, and the dyer is relieved of the many variables which affect his results in the conventional dyeing methods. The operation of this method is most simple and does not require a skilled dyer. In fact, it can be carried out with unskilled labor.

The equipment used for carrying out the method of this invention is markedly simple and inexpensive as compared with that used in the modern "continuous dyeing method. This equipment may be the same as the original reduced pad dyeing equipment discussed above except for the substitution of an acid box for the air oxidiz ing box. In other words, all that is needed is a small dye box attached to a. pad consisting of two heavy squeeze rollers, an acid box adjacent lulose ether is poured into the dye box and the cloth is passed through it, then through the squeeze rolls that press the dye into the cloth and squeeze ofl the excess dye, and then into the acid box which contains an aqueous solution of a suitable acid for "souring the cloth, that is, precipitating the dyed cellulose ether onto the cloth as described above. Examples of suitable acids are sulfuric, acetic, and formic acids. Following the soaring operation, the wet, dyed cloth is washed and dried in conventional manner.

The cellulose ether as used in my invention is in the form of a white, fiuffy, fibrous material, resembling cotton linters in appearance. This solid cellulose ether product is chemically an ether having a structure of X--OR where X represents a cellulosic unit and R one of the various alkyl or aryl groups. In usual commercial practice, these latter groups are methyl, ethyl, hydroxy ethyl and benzyl groups. These others are commonly prepared by reacting cotton linters or sulfite pulp with either inorganic acid esters, ethylene oxide, or mono-chlor acetic acid, in the presence of alkali. The solubility of the others so produced depends upon the degree of substitution. The lower are alkali soluble, intermediate are water soluble, and highest substituted are organic solvent soluble. The form that is insoluble in vwater and soluble in alkali is preierred for use in the method of the present invention. A commercially advantageou example thereof is hydroxy ethyl cellulose.

Dyestuffs that may be used for dyeing the solid cellulose others for the purposes oi this invention comprise, practically speaking, any and all dyestuifs used for dyeing cellulosic fibers. They infilaments, yarns and fabrics. These comprise the cellulosic materials of cotton, linen, hemp, jute, etc., and the regenerated celluloses or rayons; also, the cellulose esters, e. g., cellulose acetate. The synthetic fibers or materials comprise the thermoplastic, long chain linear polyamides, vin. yl resin fibers, and glass fibers.

For obtaining the alkali solution of the predyed cellulose ether, any suitable alkali may be used. Illustrative examples are sodium hydroxide and potassium hydroxide.

Regarding the predyeing of the cellulose ethers, prior to their being dissolved in alkali, the methods and means commonly employed in the dyeing of raw stock bulk cotton, may be used. Conventional equipment is a tub or circulating machine in which the solid, usually finely divided, cellulose ether is placed and a solution oi. the dyestufl is run in and circulated or stirred to efiect thorough mixing and impregnation of the cellulose ether with the liquid dyestuif. Next the dyed cellulose ether is washed and soaped in a manner conventional to raw stock dyeing. The resulting dyed cellulose ether may then be used directly, in wet form, for dissolving in alkali to produce the dyestufl. solution. However, if the dyed cellu-' lose ether is to be shipped before use in the dyeing operation it will usually be of practical and economic advantage to dry the dyed cellulose ether partially or completely, and subsequently dissolve it in alkali at the time and place of use.

In the following illustrative but non-limiting Exmn I.--NArnrnor. Ran

The dry solid cellulose ether materialis treated with the dissolved naphthol developer or prepare, Color Index No. Pr. 313, in a tub or circulating machine, such as for example a cotton raw-stock dyeing machine. In this operation the fibrous cellulose ether material absorbs the naphthol, following which the material is washed with a salt solution, or centrifuged, to remove the excess naphthol dye. The material is then treated promptly with a diazotized color base or'a dissolved color salt (for example,naphthol red base, Color Index No. Pr. 270) which combines with the absorbed'naphthol, producing'an insoluble red dyestuif. Next, the product is washed and soaped in the usual manner for raw stock dyeing, and finally the stock is dried in asuitabie manner. The final product is a dry, solid, fibrous material, dyed a fast red color.

EXAMPLE II.AumnAoumoNs Var Burn The cellulose ether is dyed in this case by treatment in a tub or circulating machine with anthraquinone vat blue, Color Index No. 1113. The dispersed vat blue paste is well mixed with the cellulose ether in the circulating machine and is reduced with a suitable amount of sodium hydrosulfite and sodium hydroxide; the amounts used being controlled to give the depth of desired shade. The leuco compound thus formed is absorbed by the cellulose ether which is then washed and oxidized in a manner similar to raw stock cotton dyeing, using, for example, sodium perborate as an oxidizing agent. The material is finally soaped and rinsed. The thus treated product is then dried, and is in the form of a dyed, blue fibrous material.

EXAMPLE III-DmrcrGnssn Exsurrr: IV-Surrua COLOR The cellulose ether is treated in thislcase with a sulfur, black, dye, Color Index No. 978, which is applied to the fibrousmaterial in a manner similar to dyeing of raw stock cotton. Afterthe cellulose ether material has been thoroughly and uniformly dyed with the sulfur-color, it is salted with sodium chloride in the regular manner and then washed and dried.

To use the predyed cellulose ether army of assault cellulose ether and dye components of the resulting solution do not separate. ,Another; type of hydroxy ethyl cellulose, which is prepared by a different chemical process, does not require freezing temperatures of the alkali to eifect solution. Instead, this cellulose ether, even after dyeing, will dissolve in caustic alkali at atmospheric temperature.

One of the highly unexpected and unique features of the above described dissolving of the predyed cellulose ether is that the completely developed dyestuif dissolves, or flnely disp erses, in the alkali. It is well known in the dyeing art that dyes such as vats or naphthols which have been oxidized or otherwise converted to final insoluble form are not soluble in alkali. Nevertheless, the predyed cellulose ether containing the dye in the finished and normally insoluble state, may be dissolved readily in the alkali, and the dye remains so closely attached to the cellulose ether that separation, even upon centrifuging, does not occur to any substantial extent.

Now, to carry out the dyeing operation on fabrics or other textile materials wlththe alkali solution of predyed cellulose ether, the dye is padded on the fabric, using thesimple,*inexpensive equipment described above, and the dyed fabric is fsoured" in an acid solution, such as a 2% solution of sulfuric acid. If desired, the dyed fabric may be rolled-up directly after the squeeze rolls and subsequently soured on a jig. Following the souring treatment the fabric is usually washed with a mild soda ash and soap solution to remove the remaining free acid. After this washing treatment the fabric isthen dried andis ready foruse. A i

Examples of commercial dyeings made in ac- ;zordance with the above procedure areas folows:

In each of the runs, the same essential operating conditionswere used. Asingle dip and single nip with seven tons roll pressure was used on the pad. After padding, the fabric was passed through two acid boxes containing 5% acetic acid deg. F.) and then into a series of four wash boxes, the first of which contained coldwater and each of the following hot'water deg. F.) and spray. Roll speed was maintained at 50 "yards perminute. F 1

Stock'solutions of 6% dyed hydroxy ethyl cellulose in 5% causticwere used tomake upflthe dye' ba'ths. Dilution with water wasmade" to eiiect the proper dye concentration. Formulations for each of the five runs are as follows? Yellow 1 .13, Pounds Yellow, predyed cellulose ether, (6% solution V .130 water 7 Pink Pounds Pink, predyed cellulose ether (6% solution) 22.5 Yellow, predyed cellulose ether (2.6% solution) 17.0 Caustic solution (50% NaOH) 6.0 Water 254.5

Blue

Pounds Blue, predyed cellulose 'ether (6% solution) 22.5 Jade Green, predyed cellulose ether (6% solution) 17.5 Caustic solution (50% NaOH) 4.0 Water 256.0

' 300.0 Green Pounds Jade Green, predyed cellulose ether (6% solution) 102.0 Blue, predyed cellulose ether (6% solution) 17.0 Caustic solution (50% NaOH) 4.0 Water 177.0

Tan

Pounds Brown, predyed cellulose ether (7% solution) 13.6 Yellow, predyed cellulose ether (2.6% solution) 120.0 Jade Green, predyed cellulose ether (6% solution) 2.4 Caustic solution (50% NaOH) 4.0 Water 160.0

Fabrics dyed in accordance with the above examples, when compared with the same fabrics dyed in a conventional manner, show not only a substantial improvement in uniformity of shade but also a striking improvement in fastness of color upon accelerated exposure to light. This is especially true of the light yellow and other pastel shades of vat dyes, which show excellent light fastness when applied in accordance with this invention.

The method of this invention has been described hereinabove with particular reference to the uniform dyeing of short yardages of cloth, such as 100 yards or less. because the problem of obtaining uniformity of shade on short lengths is especially troublesome, and is overcome by this method. Nevertheless, it is to be understood that the method and invention are not limited to short lengths but may be used on any desired length of textile material, including runs of hundreds of thousands of yards of cloth such as are commonly dyed in the "continuous dyeing" methods described above, but requiring substantially simpler equipment than the expensive continuous dyeing machines.

In addition to the above described feature of this invention of obtaining uniformity in shade from one end of the cloth to the other, the invention also has the advantage of reproducing these same uniform shade results in different lots of cloth and in different runs made at different times.

Another commercially valuable property of the method of this invention is that the alkali solutions of predyed cellulose ether may beused for effecting substantially unifonn dyeing of textile materials containing mixed fibers; that is, (ill-- ferent cellulosic fibers or mixtures of cellulosic and synthetic fibers. Although these mixed fibers may show some selectivity for the dye they will dye substantially uniformly.

For purposes of identification, the term "predyed cellulose ether as used herein, means cellulose ether dyed in solid form before it is dissolved to produce a dye solution.

Various modifications and changes may be made in the products, materials, and methods described hereinabove without departing from the scope of this invention, some of the novel features of which are defined in the appended claims.

I claim:

1. A method of dyeing textile material with dyed alkyl cellulose ether, which cellulose ether is originally in finely divided, fibrous form and is dyed by subjecting it in the solid state to the dissolved dyestuffs and developing solutions suitable for dyeing raw stock cotton and thereby producing a dyed cellulose ether in completely developed condition, comprising dissolving said dyed alkyl cellulose ether in an aqueous caustic alkali solution, treating the textile material with this alkali solution, treating the textile material with an acid solution that precipitates the dyed alkyl cellulose ether onto the fibers of the textile material, washing and drying the textile material.

2. A method of dyeing textile material with dyed hydroxy ethyl cellulose, which cellulose is originally in finely divided, fibrous form and is dyed by subjecting it in the solid state to the dissolved dyestuffs and developing solutions suitable for dyeing raw stock cotton and thereby producing a dyed hydroxy ethyl cellulose in completely developed condition, comprising dissolving said dyed hydroxy ethyl cellulose in an aqueous caustic alkali solution, treating the textile material with this alkali solution, treating the textile material with an acid solution that precipitates the dyed hydroxy ethyl cellulose onto the fibers of the textile material, washing and drying the textile material.

'3. A method of dyeing textile material with dyed alkyl cellulose ether, which cellulose ether is originally in finely divided, fibrous form and is dyed by subjecting it in the solid state to a vat dye and oxidizing said dye, comprising dissolving said vat dyed alkyl cellulose ether in an aqueous caustic alkali solution, treating the textile material with this alkali solution, treating the textile material with an acid solution that precipitates the vat dyed alkyl cellulose ether onto the fibers of the textile material, oxidizing, washiu g and drying the textile material.

4. A method of dyeing textile material with dyed alkyl cellulose ether, which cellulose ether is originally in finely divided, fibrous form and is dyed by subjecting it in the solid state to the dissolved dyestuffs and developing solutions suitable for dyeing raw stock cotton and thereby producing a dyed cellulose ether in completely developed condition, comprising dissolving said dyed alkyl cellulose ether in an aqueous caustic alkali solution, padding the textile material with this alkali solution, treating the textile material with an acid solution that precipitates the dyed alkyl cellulose ether onto the fiber of the textile 9 material, washing and drying the textile material.

5. An aqueous caustic alkali solution of dyed alkyl cellulose ether, which ether-has been previously dyed in the solid state and is insoluble in water, said dyed alkyl cellulose ether being in completely developed state, and said solution being adapted for dyeing textile material by padding and acidifying at atmospheric temperatures.

6. A method of dyeing textile material with dyed alkyl cellulose ether, which cellulose ether is originally in a flufiy, fibrous solid, water insoluble, alkali soluble, form and is dyed by subjecting it in the solid state to the dissolved dyestuffs and developing solutions suitable for dyeing raw stock cotton and thereby producing a dyed cellulose ether in completely developed condition, comprising dissolving said solid dyed alkyl cellulose ether in an aqueous caustic alkali solution, treating the textile material with this alkali solution, treating the textile material with an acid that precipitates the dyed cellulose ether onto fibers of the textile material, washing and drying the textile material.

'7. A method of uniformly dyeing textile material in pastel shades of vat dyestufls, with water insoluble, alkali soluble, hydroxy ethyl cellulose which is predyed with a vat dye by subjecting the flufly, fibrous solid hydroxy ethyl cellulose to a vat .dye and oxidizing the dye, and thereby producing an oxidized vat dyed hydroxy ethyl cellulose, comprising dissolving said vat dyed hydroxy ethyl cellulose in an aqueous caustic alkali solution, treating the textile material with this alkali solution, then treating the textile material with an acid that precipitates the vat dyed hydroxy ethyl cellulose onto the fibers oi the textile material, washing and drying the textile material.

8. An aqueous caustic alkali solution of dyed alkyl cellulose ether, which ether has been previously dyed in the solid state with a vat dye and is insoluble in water, said vat dyed alkyl cellulose ether being in completely oxidized state, and said v solution being adapted for dyeing textile material by padding and acidifying at atmospheric temperatures. l

9. An aqueous caustic alkali solution of dyed hydroxy ethyl cellulose which has been predyed in the solid state with a vat dye and oxidized, said predyed hydroxy ethyl cellulose being insoluble in water but uniformly dissolved in the alkali and does not separate to a substantial extent upon centrifuging, and said uniform solution being adapted for dyeing textile material by padding and acidifying at atmospheric temperatures.

- WILLIAM B. CARROIL, JR. 

